The invention concerns a blank, in particular a dental blank, for the production of a tooth prosthesis. The blank comprises a bed of a first material, and at least one core region which is embedded in the bed and which has a different color from the bed and comprises a second material. The core region has a surface directed in the direction of the bed.
Blanks for the production of a tooth prosthesis, which are made from various materials (for example various plastics) have already been known for some time.
There are, for example, cylindrical disks which in the axial direction comprise various layers of graduated shaded colors. In that way, it is possible to achieve a more natural color variation in dental restoration procedures.
An example of such a variant is disclosed in DE 10 2011 055 393 A1. That specification discloses the manufacture of a blank for artificial teeth, wherein the blank has a homogeneous color transition and the artificial teeth produced from the blank come close to the appearance of natural teeth. There are no visible separation lines at which it is possible to see the color transition between two materials which are of different colors. It is admittedly possible for the various profiles or structures of the plastic layers to be uniformly or non-uniformly distributed, to be of a wave-shaped, pyramid-shaped, cylindrical or cuboidal configuration, in which case however those structures which are important for manufacture can no longer be seen at all or can scarcely be seen in the finished blank due to the homogeneous color transition.
In a similar fashion, German patent DE 197 14 178 C2 describes a process for the production of a multi-colored shaped body for further processing to constitute tooth restoration, wherein there is a continuous color gradient as an essential feature.
In comparison, the invention further concerns a blank having a boundary layer delimiting the bed relative to a surface of the core region, that is directed in the direction of the bed. The boundary layer simulates a dentine boundary between a tooth enamel and a dentine. More specifically, in that case, the color graduation simulating the dentine core or the dentine boundary is produced in a certain approximation to reality from the point of view of shape.
An example of such a blank with an intentionally produced, relatively sharp dentine boundary is the so-called Vitablocs which are available on the market. They are generally of a size corresponding to a tooth so that an individual tooth or a dental prosthesis can be produced from that block.
U.S. Pat. No. 4,970,032 is known from the state of the art, describing multi-colored dental blanks, wherein individual teeth which have different color graduations are also produced.
A further specification disclosing a multi-colored dental blank is WO 2008/083358 A1. What is essential therein is that the different colored zones are arranged concentrically.
A further protection right with a shapeable blank involving different colors is WO 02/09612 A1.
DE 10 2013 203 750 A1 discloses a process for the production of a tooth prosthesis. This involves the preparation of reference data of optical properties of different dentine materials and translucent enamel materials of the tooth prosthesis. Target values are ascertained therefrom, in accordance with which a dental prosthesis shaped block having the desired boundary surface is selected and prepared by means of material removal.
DE 20 2009 018 724 U1 describes a shaped body comprising a material which is stabilized in respect of shape, and a process for the production thereof. This quite generally involves a second component being of a different pigmentation from the first component and the second component being arranged in the first component, with the formation of an interface, in such a way that the interface represents a spatially curved surface (for example a parabolic boundary line). The interfaces of the enamel-dentine boundary layers of the upper jaw and lower jaw teeth are assembled by means of a graphic software and the interface shape is generated in that way. That is very complicated and expensive and in practice has to be separately established and produced for each individual blank.
A disadvantage with the processes known from the state of the art is the relatively high level of complication and expenditure, in particular if a plurality of parts of a denture set or a plurality of teeth are to be produced.